// 位 位移
// 超出部分取出，重新拼接
let xIndex = 3

let buf = Buffer.from('123ABC')
let bufLength = buf.length

let resBuf = Buffer.alloc(bufLength)

console.log(buf)
buf.copy(resBuf, 0, xIndex, bufLength)
buf.copy(resBuf, bufLength - xIndex, 0, xIndex)

console.log(resBuf.toString('ascii'))
